1. Field of the Invention
The invention relates to a process for preparing organopolysiloxanes comprising aminoalkyl groups.
2. Background Art
Organopolysiloxane oils bearing aminoalkyl groups, referred to hereinafter as “amine oils,” are some of the most important organically functionalized organopolysiloxanes, and are used successfully in many different fields of application. These include textile finishing, architectural protection, cosmetic formulations, and the treatment of surfaces. In most applications in these fields, it is important to use amine oils which have a high quality.
Amine oils are usually prepared by condensation and/or equilibration reactions between linear or cyclic organopolysiloxanes and aminoalkyl-functionalized alkoxysilanes, or partial or full hydrolyzates thereof, usually under the action of catalytic amounts of basic inorganic or organic compounds.
According to the current state of the art, amine oils are prepared in a so called batchwise process, i.e. campaign by campaign in batchwise processes in stirred apparatus. A stirred apparatus is very flexible as a result of the variety of chemical reactions that can be performed therein. Batch processes, however, become uneconomical in the case of very large production campaigns and high mass throughputs. This is because, in particular, long times have to be accepted for heating and cooling and for filling and emptying of the vessels, which are several cubic meters in size, thus resulting in high operational expenditure and high labor costs.
A difficulty in current amine oil syntheses is the deactivation of the condensation or equilibration catalyst. When the basic catalyst is neutralized with an acid in a conventional manner, as described, for example, in U.S. Pat. No. 5,077,421, precipitation of salts causes turbidity. An additional filtration step is therefore required. In this batch process, this leads to longer plant occupation times.
One means of avoiding such turbidity is to deactivate the tetraalkylammonium hydroxides or ammonium phosphates and borates by thermal decomposition, after the reaction has ended, as described, for example, in U.S. Pat. No. 4,652,662 (corresponding to DE-A 3418358). However, the decomposition products thereby obtained have to be removed by distillation under reduced pressure. As a result of catalyst deactivation, higher temperatures are needed in this batch process, which leads to longer cooling times before the next batch can be run, which again in turn has the consequence of longer plant occupation time.
U.S. Pat. No. 7,129,369 (corresponding to EP-A 1580215) describes a process in which, in spite of the use of alkali metal hydroxides and alkoxides, turbidity-free amine oils are obtained without a filtration step, by neutralizing with silyl phosphates, which affords silicone-soluble neutralization products. This process is also a batch process with a long plant occupation time. Excess neutralizing agent is troublesome in the next batch after the plant has been emptied, and so the plant has to be cleaned beforehand in a time-consuming manner. If the plant is not cleaned before the next batch, either the reaction rate is slowed or a higher catalyst concentration is needed, which in this case has the consequence of poorer product quality.